1. Field of the Invention
The present invention relates generally to drafting devices and, more particularly, to a drafting device adapted to move across a support surface.
2. Description of the Related Art
Drafting devices typically include a straight edge for guiding a drafting implement such as a pencil or pen while a line is being drawn. Generally, the drafting device is held against a support surface such as a drafting board. The drafting device may have a raised handle or housing to allow the operator to better grasp the device. Examples of such drafting devices are disclosed in my prior U.S. Pat. Nos. 226,226; 232,051; 237,364; 237,693; 237,868; and 237,950.
Previously, drafting devices have incorporated a structure to move the drafting device easily across the support surface. An example of a drafting device having such a structure is disclosed in my prior U.S. Pat. No. 3,165,839. This patented drafting device included a ruler or body having at least one straight edge and a roller assembly mounted on the body and generally parallel to the straight edge for rolling movement of the body and straight edge across the support surface. The roller assembly included an axle, a pair of rollers mounted to the axle and a driving or actuating wheel mounted on the axle intermediate the rollers for turning the axle and moving the body and straight edge to a desired position. Once in position, an operator's finger is used to overlap the actuating wheel and a nonrotatable portion of the body for firmly holding the body and straight edge in position while a line is being drawn.
One disadvantage of the above patented drafting device is that the operator's finger is required to hold the roller assembly at the precise location for the straight edge. Another disadvantage of the patented drafting device is that the roller assembly rolls freely in the absence of the operator's finger and may be prone to passive movements caused by gravity, vibrations or unintended slips from handling. Therefore, a need exists for a drafting device which resists unintended rolling.